Method of and apparatus for coating paper



Oct. 13, 1942. c. J. MEARRILL 2,299,026

' METHOD OF AND APPARATUS FOR COATINGPAPER Filed Feb. 23, 1938 I Hy/ rog Patented Oct. 13, 1942 METHOD OF AND APPARATUS FOR COATING ITAPER Carie J. Merrill, Portland, Maine Application February 23, 1938, Serial No. 191,870

6 Claims.

. a uniform coating to a web with a minimum of equipment and apparatus therefor. This coating may be applied to either one side of the web, or to both sides of the web simultaneously, and after said application, the web is, or may be, passed through suitable drying means for drying both coating and web.

Many methods have been devised for applying coating and color materials to traveling webs or sheets. Most of these devices arequite complicated and are therefore expensive both to build and maintain. Much of this equipment and apparatus has heretofore been required, not necessarily to apply the coating materials to the web, but rather to insure that such coating materials after being applied are spread uniformly over the web and in the proper quantity, degree or thickness.

There are broadly, two methods for applying coating materials to traveling webs. The first and one generally used, is to either immerse the web in a bath of coating material contained in a tank by passing the web through such tank of material and depending on a certain amount of it adhering to the web, or what is more usually done is to immerse a roll in the coating material and then bring the roll in contact with the traveling web to efiect a transfer of the coating material from the roll to the web. Along with I this method there may be used a second or squeeze roll, utilized particularly when both sides of the web are coated, in which case a quantity of the coating material is allowed to accumulate on the rolls and web ahead of the point where the web passes between them, the rolls being so spaced as to attempt to predetermine the quantity of coating material which can pass between them and be carried away by the web itself.

The second method of applying coating materials is to spray them over the webl This method is very little used, and is generally unsatisfactory due to the character of coating materials commonly employed which contain considerable quantities or filler, color and other solid ingredients which rapidly clog the spray nozzles and cause generally unsatisfactory, inefficient and uneven operation.

Regardless of the method employed to get the coating on the web, it has heretofore been necessary to have considerable additional equipment in the form of oscillating brushes, scrapers,

smoothing rolls, doctors, compressed air jets and what not, either to remove the surplus coating material previously applied to the web, to smooth 4 out imperfections in said application, or both.

It is entirely obvious that any apparatus or any method which will apply directly to the web just the right quantity of coating materials, spread evenly and uniformly over its entire surface, will not require additional equipment or apparatus for smoothing out coating imperfections or to remove excess material. I have devised such an apparatus and such a method and as illustrative of my invention reference is made to the following figures:

Fig. 1 shows an apparatus for carrying out a method of applying coating to one side of a traveling web and, as illustrated, this application is made on the top or upper side of the web.

Fig. 2 shows an apparatus for carrying out a similar method of applying the coating to the bottom or under side of the web.

Fig. 3 shows an apparatus for applying coating to both sides of the web simultaneously.

Referring to Fig. 1, there is shown a traveling web or sheet W, drawn from a roll or other supply of this material. The web W passes over a guide roll 5, being drawn along by any suitable means or device such as a suction apron 8 which may be located on the far side or beyond a dryer or drying-oven utilized to remove the water from the coated web and the coating material. Friction may be applied to the guide roll 5, or to the roll of material from which the sheet is being drawn, to maintain a tension on the entire length of the web both as it passes the coating apparatus and also as it passes through the dryer oven. Other apparatus or devices may be employed to hold the web in positionsuch as an air jet 6, and deflector plate I, located between the coating apparatus and the dryer oven. However, neither the dryer nor the suction-apron, nor any web supporting or tension means forms any part of this-invention but are simply shown as customary or common apparatus employed in con-- a Jet of air or gas from this nozzle will be sharply impinged on the surface of roll 3.

In operation, roll 2 collects a quantity of coating materialfrorn tank. I, and carries it around until it comes in contact with roll 3. This roll 3 being spaced from roll 2, a predetermined amount, accumulates on its surface a certain quantity of coating material from roll 2.

Regardless of the amount of material picked up by roll 2, only a predetermined amount can be carried away by roll 3, this being determined by the space between this roll and roll 2.

Continued rotation of roll 3, brings the coating material'on its surface into proximity with the air jet 4 previously mentioned. The force of the air or other gas coming from this nozzle 4 then strips the coating material from the surface of roll 3, taking it of! the roll in the form a finely divided spray which leaves the roll at a very considerable velocity. It will be noted that the relative location of the web W, the roll 3, and the air jet 4, is such that this atomized coating material will be impinged directly on the traveling web W. The angle of impingement is inclined slightly against the travel of the web so that as the material is impinged thereon it will be distributed and spread backwardly over the web in an even and uniform layer over its entire surface.

I am aware that air Jets have been utilized to smooth the coating on traveling webs on which the coating has been previously applied in excess quantity, said jets serving the dual purpose of smoothing the material on the web and of removing any surplus or unnecessary material there'- from. Such a method and such a use of the air jet is but an expedient to alleviate a condition which my method and my apparatus avoids creating.

I am also aware that air lets have been used to dry the surface of a smoothing roll or rolls, to assist in their operation. My method however, does not require the use of smoothing rolls and I utilize air or other gas from a jet at high velocity for a totally different purpose and ac complish a totally different result than any heretofore employed.

Having applied a uniform amount of material to roll 3, and brought this material to a point where it is stripped off by air jet 4, I am able to control the amount of material which will be applied to the web W, and avoid either applying too little or too much. The atomization of the coating material as it is removed from the roll and the spreading out of this atomized material over a considerable area both lengthwise and crosswise of the web as indicated at 9. effects a further distribution and equalization of the coating material over the web and smooths out any possible imperfections or ridges which might exist on the surface of roll 3.

Should there be any tendency under abnormal conditions for ridges to form on roll 3, these ridges can only be of a very minor nature as they are immediately removed by the air Jet 4, and at no time can become accumulative by building up between rolls 2 and 3 on their upper side or between rolls 2-0 and 3a on the lower side. Such minute ridges as may possibly be formed on roll 3, are immediately broken up and atomized by the air jet 4, thereby being diflused over the web in a uniform layer avoiding previous difilculties of having said ridges transferred to "the webfwhen the web is brought directly in contact with the coating material on the roll.

The breaking up of the coating material into a finely divided spray is herein accomplished without requiring any of the coating materials to pass through small openings in a spray nozzle which they may very readily clog. The coating materials are spread out mechanically in a layer on roll 3, which layer is stripped from this roll, atomized, and impinged directly on the web in the form of finely divided globules or particles which attach themselves firmly on the surface of the web by virtue of their impingement thereon, and are spread out in a smooth, even and uniform layer requiring no smoothing or other treatment.

In Fig. 2 is illustrated apparatus for performing a method of applying coating materials .to the under side of the web, this method being much the same as that shown in Fig. 1, and the elements I, 2, 3, l, 9, HI, and I2 correspond to the elements I, 2, 3, 4, 8, l0 and I! of Fig. 1.

Fig. 3 illustrates an apparatus for performing the method utilized to apply coating materials to both sides of the web simultaneously. In this case, the web is fed over a guide roll 5, as before, and in addition to the rolls 2 and 3, with the air Jet 4 located above the sheet there are rolls' 2--a-and 3-a with air jet 4--a located beneath the web, the elements of this figure being the same as those in Figs. 1 and 2.

These three methods make it possible to coat either the exterior or interior surface of a web as it is taken from a roll or to coat both sides of the web simultaneously.

It will be observed that I direct theimpingement of the coating material on the web at an angle against the direction of the web travel. The coating materials thus applied are spread back over the web as it approaches the point of impingement and ample space is given for the air and coating material to separate enabling all of the material impinged on the web to be retained thereby, and the air to become separated therefrom. By having only sufficient amount of coating material on the surface of rolls 3 and 3-a.

I I am thus able to apply all of this material to the surface of the web with no necessityof afterward removing a part of it and providing means for the disposal of said removed materials.

I may revolve rolls 2 and l in either direction as bests suits the particular condition and character of coating materials utilized. Or I a may add other rolls to aid or facilitate in applylog the coating materials to roll 3 in a uniform layer.

While I disclose one method of applying the coating materials to roll 3, it is obvious that other methods can be utilized if desired, so long as said method applies to roll 3 a reasonably uniform coating over its entire surface.

Figs. 1, 2 and 3, show a dryer for removing the moisture from the web and coating thereon after application. This dryer may be of any conventional design or arrangement and its detail construction forms no part of this inven The web may be moved through the dryer and past the point of coating application by means of a suction apron 8, previously mentioned, sufllcient friction or retarding action being applied to roll 5, or at some point back of the point of coating application to maintain the web W under some tension.

To maintain the -web position relative to the coating mechanism there may be provided an air nozzle 6, with deflecting apron or shield' I, the function of which is to; maintain theweb flat and in a substantially fixed, vertical position relative to the rolls 3' and 3a and. thejets :4 and 4a.

In instances where the web, is coated only on one side, it is possible to employ additional guide rolls on the uncoated side. However, I prefer to use the jet and deflector guiding method as shown. It is of course obvious that this may be applied to more than one point in web travel and could, if necessary or desirable, be applied both above and below the web.

Mention has already been made of the simplicity of the apparatus herein disclosed, and the directness by which it accomplishes its, objective. In addition to this other advantages are obtained. It is frequently desirable to vary the amount of coating materials applied to a traveling web or to change the speed of .the web travel to facilitate the carrying out of certain other operations such as the drying of the'coating materials and web, or the finishing of the dry web. Heretofore, such desirable adjustments could only be made with considerable difficulty, due to the complicated nature of the coating and smoothing apparatus and the inability to control very accurately, either the amount of the material applied to the web initially, or the amount of material removed from the web by the smoothing operation.

The apparatus herein disclosed provides a direct and immediate method for accurately controlling the amount of coating material applied to the web and of varying at will the amount of this material, or the speed of web travel with the same amount of material. 4

For instance, should it be desired to increase the amount of coating material supplied to the web, it is simply necessary to increase the speed of rotation of rolls 2 and 3, relative to the web speed, as the roll 3 will then bring coating material at a more rapid rate to air jet 1, to be atomized and impinged on the web in increased sired to decrease the amount of coating material supplied to the web, it will simply be necessary to decrease the speed of rolls 2 and 3, relative to the speed of web travel.

If it is desired to change the speed of the web for any reason it is readily possible to maintain the same quantity of .coating material on its surface, by changing the speed of rolls 2 and 3 simultaneously with a change in web travel speed, thereby-delivering the same quantity of material per unit length of web regardless of the change of rate of web travel.

It is therefore obvious that I have provided not only a very simple and efllcient method for applying coating to a traveling web, but have also provided an apparatus which inherently permits it to be readily adaptable and adjustable to meet the varying conditions and requirements of commercial use.

Having thus described my method and apparatus, what I claim is:

1. Apparatus of the class described for applytraveling web, comprising a tank for containing said coating materials, a roll partially immersed in the coating materials in said tank, means to from said first roll, means to rotate said second roll, means for moving the web past said rolls and a nozzle extending in. proximity to said second and directed toward said web at an angle effective when a jet of air said materials during said removal, and the im-/ pingement of said atomized materials on the surface of a traveling web. V

3. The method of coating a traveling webwhich comprises removing a measured quantity of semi-liquid coating material from a source of supply, transferring said, measured quantity to a moving surface by depositing said material on the moving surface in a layer of predetermined thickness, impinging a jet of air against said layer of coating material at an angle opposed to the ,7 quantity and thickness. Similarly, if it is depath of travel of the web, said angle being such that the coating material will be removed from the moving surface and deflected to said travelins web in an even and uniform layer over the surface of the web.

4. The method of coating a traveling web which comprises removing a measuredquantity of semi-liquid coating material from a source of supply, transferring said measured quantity to a moving surface by depositing said material on the moving surface in a layer of predetermined thickness, impinging a jet of air against said layer of coating material at an angle opposed to the path of-travel of the web, said angle being such that the coating material will be removed from the moving surface and deflected to said traveling web in an even and uniform layer over the surface of the web, and during such deflection atomizing the material to facilitate even distribution thereof over the traveling web. Y 5. An apparatus of the class described for applying semi-liquid coating material to a travel his web, comprising a tank containing said material, a roll rotatably mounted in said tank, and positioned to pick up said coating material upon rotation, a second roll rotatably mounted in closely spaced relation to said first roll in position for said first roll to transfer a predetermined quantity of the coating material thereto in a layer of a thickness determined by the spacing, and means, including a nozzle positioned to -00; impinge a jet of air against the layer of coating lng coating materials in semi-liquid form to a rotate said roll, a second roll mounted out of I contact with the coating materials in said tank and fixed at a predetermined distance from said first roll, effective to receive coatingmaterial in semi-liquid form of a predetermined thickness material on said second roll, to strip same from the roll, said nozzle being mounted at an angle effective to direct the'iet of air towards the second roll to remove the layer from the roll surface and deflect same against the traveling web,

and said nozzle being shaped and proportioned 7 spaced relation to said first roll and spaced mounted at an angle effective to direct the jet of air or gas in opposition to the path of travel of the web and towards the second roll, to remove the layer from the roll surface and deflect the coating material against the traveling web, in an even and uniform layer over the surface of the web.

CABLE J. MERRILL. 

